/Engine/Plugins/Experimental/MeshModelingToolsetExp/Source/MeshModelingToolsEditorOnlyExp/Public/SkeletalMesh/SkinWeightsPaintTool.h
Applies an edit to a single vertex weight on a single bone, then normalizes the remaining weights while keeping the edited weight intact (ie, adapts OTHER influences to achieve normalization)
void EditVertexWeightAndNormalize ( const int32 BoneIndex, const int32 VertexId, float NewWeightValue, [FMultiBoneWeightEdits](API\Plugins\MeshModelingToolsEditorOnlyExp\SkeletalMesh\FMultiBoneWeightEdits) & WeightEdits )